The measurement of oxygen concentration in the presence of other gases is a problem of current interest, particularly in the medical field. The method of oxygen measurement most commonly used in the prior art is a "Clark" electrode cell such as that described in L. C. Clark, "Monitor and Control of Blood and Tissue O.sub.2 Tension", Trans. Am. Soc. Artif. Int. Organs 2 41-46 (1956). These cells must be recalibrated often, and their use involves the repeated handling of filling solutions and delicate membranes. Other methods which have been explored for the measurement of oxygen include mass spectrometers and gas chromatographs, paramagnetic measuring techniques, solid state electrochemical devices, fluorescent quenching, and colorimetric methods. None of these methods has proven completely acceptable for oxygen measurement, particularly, in medical applications.
In U.S. patent application Ser. No. 805,551 filed by Jacob Y. Wong on June 10, 1977, entitled Measuring Gaseous Oxygen with UV Absorption (assigned to the present assignee), issued on June 20, 1978, as U.S. Pat. No. 4,096,388 there is described a system in which the spectral emission from a UV source is broadened to include different wavelengths which are either strongly or weakly absorbed by O.sub.2 but are about equally absorbed by other gases. An etalon filter selectively passes the wavelengths through an oxygen containing sample, whence the difference in absorption of the two wavelengths provides an indication of the amount of O.sub.2 in the sample. A device using this scheme requires an elaborate Fabry-Perot etalon filter for its operation, which is undesirable in certain applications.